During an Apple Sales Web webcast earlier today discussing MobileMe, Apple employee Maxime Veron mentioned that iTunes 7.7 would be available "in a few hours."
Keep checking iTunes and Software Update for more info.
Update: As of 6:05 PM EDT, no update was available. If this is tied to the MobileMe push starting at 9:00 PM EDT, we may begin seeing iTunes 7.7 at that time. This is, of course, pure speculation.